Torsional ultrasound handpiece

ABSTRACT

A handpiece having at least one set of piezoelectric elements. The piezoelectric elements are constructed of segments that produce both longitudinal and torsional motion. An appropriate ultrasound driver drives the set of elements at the respective resonant frequencies to product longitudinal vibration and torsional oscillation.

This application is a continuation-in-part application of U.S. patentapplication Ser. No. 09/106,223, filed Jun. 29, 1998 now U.S. Pat. No.6,077,285.

This invention relates to ultrasonic devices and more particularly to anophthalmic phacoemulsification handpiece.

BACKGROUND OF THE INVENTION

A typical ultrasonic surgical device suitable for ophthalmic proceduresconsists of an ultrasonically driven handpiece, an attached hollowcutting tip, an irrigating sleeve and an electronic control console. Thehandpiece assembly is attached to the control console by an electriccable and flexible tubings. Through the electric cable, the consolevaries the power level transmitted by the handpiece to the attachedcutting tip and the flexible tubings supply irrigation fluid to and drawaspiration fluid from the eye through the handpiece assembly.

The operative part of the handpiece is a centrally located, hollowresonating bar or horn directly attached to a set of piezoelectriccrystals. The crystals supply the required ultrasonic vibration neededto drive both the horn and the attached cutting tip duringphacoemulsification and are controlled by the console. The crystal/hornassembly is suspended within the hollow body or shell of the handpieceat its nodal points by relatively inflexible mountings. The handpiecebody terminates in a reduced diameter portion or nosecone at the body'sdistal end. The nosecone is externally threaded to accept the irrigationsleeve. Likewise, the horn bore is internally threaded at its distal endto receive the external threads of the cutting tip. The irrigationsleeve also has an internally threaded bore that is screwed onto theexternal threads of the nosecone. The cutting tip is adjusted so thatthe tip projects only a predetermined amount past the open end of theirrigating sleeve. Ultrasonic handpieces and cutting tips are more fullydescribed in U.S. Pat. Nos. 3,589,363; 4,223,676; 4,246,902; 4,493,694;4,515,583; 4,589,415; 4,609,368; 4,869,715; and 4,922,902, the entirecontents of which are incorporated herein by reference.

When used to perform phacoemulsification, the ends of the cutting tipand irrigating sleeve are inserted into a small incision ofpredetermined width in the cornea, scera, or other location in the eyetissue in order to gain access to the anterior chamber of the eye. Thecutting tip is ultrasonically vibrated along its longitudinal axiswithin the irrigating sleeve by the crystal-driven ultrasonic horn,thereby emulsifying upon contact the selected tissue in situ. The hollowbore of the cutting tip communicates with the bore in the horn that inturn communicates with the aspiration line from the handpiece to theconsole. A reduced pressure or vacuum source in the console draws oraspirates the emulsified tissue from the eye through the open end of thecutting tip, the bore of the cutting tip, the horn bore, and theaspiration line and into a collection device. The aspiration ofemulsified tissue is aided by a saline flushing solution or irrigantthat is injected into the surgical site through the small annular gapbetween the inside surface of the irrigating sleeve and the outsidesurface of the cutting tip.

There have been prior attempts to combine ultrasonic longitudinal motionof the cutting tip with rotational or oscillating motion of the tip, seeU.S. Pat. Nos. 5,222,959 (Anis), U.S. Pat. No. 5,722,945 (Anis, et al.)and U.S. Pat. No. 4,504,264 (Kelman), the entire contents of which areincorporated herein by reference. These prior attempts have usedelectric motors to provide the rotation of the tip which require O-ringor other seals that can fail in addition to the added complexity andpossible failure of the motors.

Accordingly, a need continues to exist for a reliable ultrasonichandpiece that will vibrate both longitudinally and torsionally.

BRIEF SUMMARY OF THE INVENTION

The present invention improves upon prior art ultrasonic devices byproviding a handpiece having at least one set of piezoelectric elements.The piezoelectric elements are constructed of segments that produce bothlongitudinal and torsional motion. An appropriate ultrasound driverdrives the set of elements at the respective resonant frequencies toproduce longitudinal vibration and torsional oscillation.

It is accordingly an object of the present invention to provide anultrasound handpiece having both longitudinal and torsional motion.

It is a further object of the present invention to provide an ultrasoundhandpiece having a pair of piezoelectric elements polarized to producelongitudinal motion and a pair of piezoelectric elements polarized toproduce torsional motion.

Other objects, features and advantages of the present invention willbecome apparent with reference to the drawings, and the followingdescription of the drawings and claims.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross-sectional view of one embodiment of an ultrasoundhandpiece of the present invention.

FIG. 2 a block diagram of a first driving circuit that may be used withthe present invention.

FIG. 3 is a block diagram of a second driving circuit that may be usedwith the present invention.

FIG. 4 is a perspective view of a phacoemulsification tip that may beused with the present invention.

FIG. 5 is a cross-sectional view of the phacoemulsification tipillustrated in FIG. 4 taken at line 5—5 in FIG. 4.

FIG. 6 is a perspective view of an ultrasonic piezoelectric crystal thatmay be used with the present invention.

DETAILED DESCRIPTION OF THE INVENTION

As best seen in FIG. 1, one embodiment of handpiece 10 suitable for usewith the present invention generally has cutting tip 12, handpiece shell14, ultrasound horn 16, torsional ultrasound crystals 18 andlongitudinal ultrasound crystals 20. Horn 16 is held within shell 14 byisolator 17. Crystals 18 and 20 are held within shell 14 and in contactwith horn 16 by back cylinder 22 and bolt 24. Crystals 18 and 20 vibrateultrasonically in response to a signal generated by ultrasound generator26. Crystals 18 are polarized to produce torsional motion. Crystals 20are polarized to produce longitudinal motion.

Alternatively, as illustrated in FIG. 6, crystal 23 may be used toproduce both longitudinal and torsional motion. Crystal 23 is generallyring shaped, resembling a hollow cylinder, and is constructed from aplurality of crystal segments 25. Upper portions 27 of segments 25 maybe polarized to produce clockwise motion while lower portions 29 ofsegments 25 may be polarized to produce counterclockwise motion or viceversa. When segments 25 are assembled into crystal 23, the polarizationof segments 25 cause crystal 23 to twist when excited. In addition, thetwisting motion of crystal 23 will produce longitudinal motion, but suchlongitudinal motion will resonate at a different resonant frequency thanthe torsional motion. For example, torsional movement in crystal 23 canoccur at approximately between 18 kilohertz (Khz) and 25 Khz whilelongitudinal motion in crystal 23 can occur at approximately between 33Khz and 43 Khz, with approximately 21 Khz and approximately 38 Khz,respectively, being preferred. This difference is because the forces oncrystal 23 resisting such vibrations are different in the torsionaldirection than in the longitudinal direction. One skilled in the artwill recognize that different frequencies may be used depending upon theconstruction of crystal 23. By subjecting crystal 23 to two drivesignals, one at the torsional resonant frequency and one at thelongitudinal resonant frequency, both torsional and longitudinal motioncan be produced in crystal 23. Handpiece 10 may can any suitable numberof pairs of crystals 23, for example a single pair or two pairs.

As seen in FIG. 2, ultrasound generator 26 employs a broad-spectrumsource to generate at least a component of the signal that drives anultrasonic handpiece (“the drive signal”). The broad-spectrum source maybe programmable and thus easily adjustable by varying certain inputinformation fed to the source. However, a fixed-spectrum source may alsobe used without difficulty. A fast fourier transform (“FFT”) digitalsignal processor (“DSP”) may be used to analyze the response ofhandpiece 10 to the broad-spectrum component of the drive signal. Inreal-time applications, the output of the FFT DSP is used to generatecontrol parameters embodied within an appropriate feedback signal, whichis fed to the circuitry generating the drive signal in order to alteraspects of the drive signal. As seen in FIG. 3, ultrasound generator 26may also use a conventional signal processor to analyze the response ofhandpiece 10 to the drive signal. The term “drive signal” as used hereencompasses at least a signal useful solely for powering an ultrasonichandpiece, a signal useful solely for tuning or calibrating a handpiece,and a combination of such a power signal and such a tuning orcalibration signal.

As shown in FIG. 2, broad spectrum signal source 28 generates drivesignal 4 which is combined with drive signals 5 and 6 from torsionalsingle frequency source 30 and longitudinal single frequency source 32,respectively, in amplifier 34. Amplifier 34 delivers drive signal 36 tohandpiece 10 and to FFT DSP 38. FFT DSP 38 also receives feedback signal40 from handpiece 10. FFT DSP 38 processes drive signal 36 and feedbacksignal 40 in the manner more fully disclosed in commonly owned U.S.patent application Ser. No. 08/769,257 (corresponding to PCT PatentApplication No. PCT/US97/15952), the entire contents of which beingincorporated herein by reference, to determine the operatingcharacteristics of handpiece 10. FFT DSP 38 determines the electricalresponse of handpiece 10 on broad spectrum signal 4 and provides signal42 to DSP 39 which generates adjusting signals 60 and 61 to adjust thefrequencies and/or output voltage of sources 32 and 30, respectively soas to adjust drive signals 5 and 6.

As shown in FIG. 3, two conventional drive signal sources, such as thosedescribed in U.S. Pat. No. 5,431,664, the entire contents of which isincorporated herein by reference, or U.S. patent application Ser. No.08/769,257 (corresponding to PCT Patent Application No. PCT/US97/15952),may be used. For example, source 44 may generate drive signal 45 fortorsional crystals 18 and source 46 may generate driving signal 47 forlongitudinal crystals 20. Drive signals 45 and 47 are combined inamplifier 134 and drive signal 136 delivered to handpiece 110. Handpiecefeedback signal 140 is filtered through separator 48 to provideadjusting signals 50 and 52 to sources 44 and 46. Separator 48 may beany number of commercially available analog or digital devices such lowpass or high pass filters or heterodyne receiver.

The torsional motion of horn 16 may cause cutting tip 12 to loosen. Inorder to reduce the chances of cutting tip 12 becoming loose, tip 12 maybe asymmetrically shaped, as seen in FIGS. 4 and 5. This asymmetricshape can be accomplished by cutting spiral thread 13 in tip 12 toincrease the hydrodynamic forces on tip 12 in the manner more fullydescribed in U.S. Pat. No. 5,676,649, the entire contents of which beingincorporated herein by reference.

While certain embodiments of the present invention have been describedabove, these descriptions are given for purposes of illustration andexplanation. Variations, changes, modifications and departures from thesystems and methods disclosed above may be adopted without departurefrom the scope or spirit of the present invention.

I claim:
 1. An ultrasound surgical handpiece, comprising: a) a handpieceshell; b) an ultrasound horn held within the shell; c) at least one pairof ultrasound crystals polarized to produce longitudinal motion whensubjected to a first drive frequency and torsional motion when subjectedto a second drive frequency, the crystals held in contact with theultrasound horn; and d) a cutting tip mounted on the horn opposite thecrystals; wherein one of the frequencies is approximately between 18kilohertz and 25 kilohertz and the other frequency is approximatelybetween 33 kilohertz and 43 kilohertz.
 2. The handpiece of claim 1,wherein the cutting tip is asymmetrically shaped.
 3. The handpiece ofclaim 1, wherein the crystals are constructed of crystal segments.